A lot of any GMing is you make the rp you feel comfortable running.

Don't want to GM the monsters? Don't GM the monsters. Assign that to a Co-GM Luckily Klaxosaurs have even less 'rules' than Evangelion's Angels so you can basically have the Fraxx pilots fight anything you want, and have that thing or things act in any way you want. Melt, turn into blocks, etc.

A slice of life rp in a closed setting with ships, drama and an even number of boys and girls is considerably easier to implement. Set aside a limited number of slots for boys and girls, and whenever they're not fighting, they're builfding the characters. Downtime is important in rps. I've seen lots of rps that are nothing but downtime, but there are none that are exclusively uptime.